In a manufacturing process of a semiconductor integrated circuit, a wiring pattern is formed on a surface of a semiconductor wafer as a substrate to be processed, or contact holes between wiring are buried by depositing a metal or a metal compound such as W (tungsten), WSi (tungsten silicide), Ti (titanium), TiN (titanium nitride), TiSi (titanium silicide), Cu (copper), TaO (tantalum oxide) or the like, to form a thin film.
For example, a tungsten film forming method by using WF6 gas as a tungsten-containing gas has been proposed. In this method, an initial tungsten film forming process is performed by using one of SiH4 gas, Si2H6 gas and B2H6 gas as a reduction gas, and a passivation tungsten film forming process and a main tungsten film forming process are performed by using H2 gas as a reduction gas to thereby improve throughput and buriability of a tungsten film (for example, see Japanese Patent Laid-open Application No. 2004-273764).
In the film forming method disclosed in Japanese Patent Application Laid-open No. 2004-273764, a reduction gas used in the initial tungsten film forming process is preferably selected from SiH4 gas, Si2H6 gas and B2H6 gas depending on the property of a required film, and different kinds of processes are carried out continuously in one film forming chamber for each wafer. As such, when different kinds of processes are continuously performed in one chamber in the film forming apparatus, the residual gas used in a preceding process or deposits in the chamber can adversely affect a subsequent process, and so it is desirable to carry out a cleaning operation between the preceding process and the subsequent process. Moreover, after the cleaning operation, a precoating process that involves depositing a thin film on the inner side of the chamber is conducted to make the processing condition for the first wafer sheet parallel to the processing conditions for the second and its next wafers in the subsequent process. The process that includes such a cleaning or a precoating operation and puts the environment inside the chamber in good order is called a conditioning process, and the conditioning process that is carried out between the preceding process and the subsequent process is called an inter-process conditioning.
Generally, making a determination whether to perform an inter-process conditioning is up to a process manager. Therefore, if the process manager makes a wrong decision, for example, if a conditioning process was not performed even though it was needed, adverse effects can occur in the subsequent process. On the contrary, if the conditioning process was performed even though it was not needed, throughput of the entire film forming process is deteriorated.